1. Field of the Invention
The present invention relates to an asynchronous time division multiplex switching network for switching digital communication data, particularly multi-rate communication data, pertaining to different communication services such as telephone, data transmission, visiophony, CATV and the like.
2. Description of the Prior Art
The theory behind asynchronous time division multiplex switching systems has been considered for a switching system integrating digital telephone and communication data and defining circuit and packet hybrid frames (see FR-A-2500704 of Feb. 20, 1981). This switching system consists of terminal switching equipments (TSEs), connected on the one hand to time division multiplex highways, and on the other hand to a switching network.
FIG. 1 is a block diagram of a prior art uni-directional representation having the separate inputs i and outputs o. To switch the contents [j] of the incoming asynchronous time division channel (j) in the incoming multiplex highways MUX.sub.ip to the outgoing asynchronous time division channel (k) in the outgoing multiplex highway MUX.sub.oq, the terminal switching equipment TSE.sub.ip forms a packet (P) comprising contents [j] to which the destination address (q, k) is added and then enters this complemental packet in the switching network (R). With the help of this address, the switching network orients the packet toward terminal switching equipment TSE.sub.oq. Terminal switching equipment TSE.sub.oq inserts contents [j] into the channel (k) of outgoing multiplex highway MUX.sub.oq.
The address (q, k) is supplied by a control memory local to the terminal switching equipment TSE.sub.ip and addressed by channel (j). This memory is thus input controlled. The input control memories are economical memory-wise in capacity as seen hereafter and well suited to point-to-point connections of the type defined by EQU pj.fwdarw.qk
and to concentration communications in which a plurality of calling parties pj, p'j', p"j" require connection to a single called party qk EQU pj, p'j', p"j".fwdarw.qk
On the other hand, the control store CS may be controlled by the output. In this case, the TSE.sub.ip adds to channel (j) the number p of the incoming multiplex highway to form a set of addresses or labels (pj) which is sent to all the terminal switching equipments TSE.sub.0. Each terminal switching equipment TSE.sub.0, for example terminal switching equipment TSE.sub.oq, reads its local control store CS at address (pj) where the address k of the outgoing asynchronous channel is stored. This mode of control of the control store is well suited for diffusion communications, that is for connections of the type in which a single calling party pj requires connection to a plurality of called parties qk, q'k', q"k", i.e., EQU pj.fwdarw.qk, q'k', q"k";
however, in return, this control mode is very expensive in memory unit capacity as described hereafter.